- "He's like a lion in a cage."
- —A young Jodie, describing Aiden's presence
Aiden (pronounced "Eye-Den") (born and died on May 10, 1990) is the secondary playable character, and the invisible protagonist of Beyond: Two Souls. Along with Jodie, as protagonists, they form and refer to the title of the game. He was the son of Jonathan Nichols and Norah Gray, and the twin brother of Jodie Holmes, he died during childbirth, strangled by the umbilical cord. However, his spirit remains tethered to Jodie which allows him to communicate with her.
Aiden is an Entity that has been linked to Jodie Holmes since birth. They are connected by an Ethereal Tether, that can be seen when switching to Aiden's view. This tether acts as a spiritual link between them that keeps Aiden bound to Jodie. Though he can travel farther away in some situations, the separation causes Jodie excessive amounts of pain and lasting disorientation.
Jodie and Aiden seem to age in sync, for as Jodie grows older, Aiden grows stronger, and their bond grows greater. As the story progresses, it is revealed that Aiden is Jodie's stillborn twin brother. Jodie was delivered safely from her mother's womb, but her brother was strangled by the umbilical cord. Rather than passing on, his soul became linked to Jodie and remained that way, growing up as if it occupied a physical body.
The man Aiden would have been was shown briefly after Jodie shut down the Black Sun; however, his facial appearance was obscured. After the events of Black Sun, Aiden was separated from Jodie, causing a massive memory lapse in Jodie that spurred her to write about her experiences in a personal journal. It seems that Aiden is linked not only to Jodie's active mind, but also to her memories, which might explain why his behavior matched Jodie's so often as if they were shaped by the same experiences. Eventually, Aiden returns to Jodie, but as an entity separate and unbound.
In the final mission, Aiden gets ripped out of Jodie and gets stuck in the infra-world. Even though Aiden's soul is free, he returns and watches over Jodie, as seen in the very last scene of each ending in the game (unless you choose to live with Zoey), where the writing: "Still here" appears in front of Jodie.
Throughout the game, Aiden shows that he is capable of human emotion through his interactions with Jodie and his own frustration at the restraining tether. While his personality and actions depend on the player, Aiden genuinely cares about Jodie and will go to great lengths to protect her from harm. Jodie in turn is the only one capable of listening to or communicating with Aiden. Cole and Ryan can also communicate with Aiden when Jodie is being sedated by the CIA. However, whether she is able to control Aiden against his will is up for debate. While she often instructs Aiden in various tasks throughout the game, he usually does so willingly. Jodie does force Aiden to open up her apartment door for her in "The Dinner" when he tries to lock her out, but it required some discomfort and gave her a nosebleed. He tries to stop her when he disagrees with her, not by directly hurting her, but by making obstacles for her. It is unknown what Aiden's main goal in the game is, although he appears to think of Jodie as his charge. Still, since he is bound to Jodie, his sole purpose in life (in his case, Jodie's life) is to protect Jodie from whatever danger.
Though normally indifferent or hostile to anyone Jodie meets, Aiden greatly distrusts Ryan Clayton, to the point of destroying Jodie's laptop to prevent her from going out with him and (if the player chooses) sabotaging Clayton's visit to her apartment at every opportunity. Due to the CIA's ulterior motives, however, it appears this behavior was not completely unjustified. Nevertheless, Aiden was forced to turn to Clayton for help after Jodie had been captured and drugged by the CIA.
Powers and Abilities
As an entity, Aiden possesses a myriad of supernatural abilities, including:
Levitation: Aiden can float and hover at any height. Due to his Ethereal Tether, however, he can only travel a certain distance from Jodie.
Intangibility: Aiden can phase through any solid surface. However, he could not travel through a particular entity-proof doorway inside the Dragon's Hideout.
Aura perception: Aiden can see the auras of other people and objects, depending on how he can interact with them.
Telekinesis: With enough concentration, Aiden can deliver powerful Psychokinetic thrusts that can move physical objects and damage spiritual entities. He can also perform a Vaderian "force choke" to strangle enemies. People and objects that can be affected emit a blue aura. Enemies that can be strangled have a red aura.
Possession: Aiden can take over the minds of any nearby humans, allowing him to more directly interact with the physical world. The possessed individuals usually have rolled-back eyes and are incapable of speech. Aiden can only possess humans as long as he remains untouched by another human; this can be seen in chapters such as "Like Other Girls". Being touched by another person will cause the person's soul to reject Aiden and he will either need to find a different approach or repossess the person to accomplish the task required. When possessing an enemy, he usually simply has them commit suicide when their services are no longer needed. People that can be possessed emit an orange aura.
Clairvoyance: Psychic ability that allows him to direct mnemonic imprints from certain spots to Jodie for her to experience. Jodie in turn can see the world from Aiden's point of view, and used this ability to copy classified documents while inside the embassy.
Mind Linking: Aiden shows an ability to link Jodie's consciousness to another person's, allowing her to communicate with them if they are otherwise unable to communicate. When used on Norah, the effect was temporary due to the drugs she was given.
Mediumship: Aiden can "read" the souls of deceased human beings, using Jodie as a mouthpiece to deliver their message.
Healing: Aiden can heal Jodie and the people who Jodie directs him to heal by greatly speeding up their healing process and relieving the pain. However, the only healing notably done was wound-healing and cold-relieving (Easing Jimmy's shivering, possibly due to withdrawal from drugs). People in need of medical attention and their afflicted areas appear in green.
Force field: Aiden is capable of creating a protective field that can shield Jodie from harm like bullets and fire, as well as break Jodie's fall from potentially lethal heights. Aiden creates the field only on Jodie, but is still capable of protecting other people, like Salim and Tuesday.
Pyrokinesis: He is also shown to have a certain control over fire, such as turning down the flames in a burning building to allow Jodie to escape, and lighting a campfire in Dragon's Hideout.
- The name "Aiden" comes from the word "aed" which means "fiery, little fire" in Gaelic. 
- Aiden is pronounced /ˈaidᵊn/ as opposed to /'eidᵊn/.
- Oddly his name will be mispronounced several times.
- Nathan pronounces it the latter way, during The Condenser.
- In the chapter Like Other Girls, Nathan can say his name incorrectly if Jodie is caught before she and Cole leave the parking lot,
- If Jodie took revenge on the teens in The Party.
- When Jodie is about to leave for the CIA , Nathan will say it incorrectly again. (Determinant)
- Jodie can also mispronounce his name in the chapter Dragon's Hideout.
- Oddly his name will be mispronounced several times.
- In the chapter Navajo, though it is very faint, Aiden will say goodnight to Jodie on the First Night. 
- If Aiden was born alive, he would have been adopted by another family.